The present invention relates to an alarm system capable of bidirectionally transmitting an alarm signal representative of any of emergency conditions such as a fire, a burglary and the like between a central station and a plurality of subscribers' stations through a bidirectionally transmissible line interconnecting the central station and the respective subscribers' stations, and more particularly to such an improved alarm system effectively utilizing the existing bidirectional wired TV system.
Prior art alarm systems constructed to present an emergency alarm service to any of the customers of a community antenna TV system (hereinafter referred to as "CATV" system) generally have the disadvantage that they are considerably complicated and expensive in construction.
For example, a prior art alarm system constructed to take up an image representative of an emergency condition such as a fire, a burglary or the like transmitted from any of the subscribers' stations by an ITV camera in a central station and then to transmit the take-up image to the respective subscribers in a forced interrupting operation requires a particular ITV camera in the central station and a forced power supply closing device and a forced channel interrupting device in the respective subscribers' stations. Consequently, such a prior art alarm system has the disadvantages that it is necessary to modify the respective subscribers' TV receivers and the supervisor must be available at the central station since the reception of an emergency alarm signal from any of the subscribers' stations and the response thereto must be carried out at the central station.